This invention relates to arrangements for preventing the theft of motor vehicles, and more particularly, to a protection system for preventing a motor vehicles from being started by an unauthorized person.
Various systems have been devised to prevent the theft of motor vehicles. The most commonly used systems cause an audible and/or visual alarm to be generated if an unauthorized person attempts to enter or tamper with a protected vehicle. Although audible and visual alarms may act as a deterrent to the theft of a vehicle, they do not prevent theft of the vehicle. Moreover, generally alarm systems of this type are subject to compromise.
Other types of vehicle anti-theft systems that have been proposed temporarily disable the vehicle on which they are installed. Such systems may be incorporated into the vehicle ignition and starter circuit, connected into the vehicle braking system, or connected into the fuel line system, for example. Although such systems are more difficult to compromise than alarm type systems, they are expensive to install because of the requirement that they be incorporated into an operating system of the vehicle. Moreover, these systems generally require some modification of operating systems of the vehicle.
In U.S. Pat. No. 4,958,084 issued to Louis D. Carlo et al., there is disclosed an anti-theft device adapted to be connected to a battery of a motor vehicle and including a power switch for disconnecting the battery from its standard battery cable when current flowing through the cable exceeds a preselected current that is associated with an attempt to start the vehicle. A override circuit is effective to override the operation of the power switch to permit the vehicle to be started.